Viewers in Asia, Australia, Europe and Africa were treated to a very subtle type of eclipse Friday (Jan. 10) — a penumbral lunar eclipse (opens in new tab) that just barely darkened the moon.
The Wolf Moon (opens in new tab) passed through the faint outer shadow of the Earth, which is called the penumbra, and made the moon's usual black, gray and white tones take on a tea-stained color (opens in new tab). The eclipse took place over four hours starting at 12:07 p.m. EST (1707 GMT), with maximum eclipse occurring at 2:10 p.m. EST (1910 GMT).
"You can see this isn't an evenly illuminated full moon (opens in new tab), but it's getting more and more difficult to see now," said Slooh astronomer Paul Cox around 3:30 p.m. EST (2030 GMT), during a live astronomy broadcast as the eclipse was nearing its last phases.
Photo Gallery: See the Wolf Moon Lunar Eclipse in Amazing Pictures! (opens in new tab)
Related: Lunar Eclipse 2020 Guide: When, Where & How to See Them (opens in new tab)
Cox pointed out the penumbral eclipse to viewers using a live telescope view of the moon, from the Canary Islands. "Down at the bottom right hand corner, about the 4:00 or 5:00 position, you can see it's just darker," he explained. "[The shadow] is not like the dark seas (opens in new tab) up above, but there is a slight shade, and there is a slight curvature to it."
A penumbral eclipse happens due to a slight misalignment between sun, moon and Earth. This type of eclipse needs two key ingredients: for the moon to be at the full moon phase (which it reached at 2:21 p.m. EST, or 1921 GMT) and for the three celestial bodies to come close to aligning — close enough for the moon to pass through the outer region of Earth's shadow, but not the central part of the shadow.
When the three bodies are more tightly aligned, more spectacular eclipses happen. Partial lunar eclipses occur when the moon passes into the deeper part of the Earth's shadow (known as the umbra), and total lunar eclipses — also known as Blood Moons (opens in new tab) — happen when the Earth completely blocks the sun's light from reaching the moon. During total eclipses, the moon only receives refracted light from Earth, turning the surface red.
Solar eclipses (opens in new tab), by contrast, have to do with how perfectly the moon covers the sun in the sky when it passes in between the sun and the Earth. If the moon partially crosses over the sun, a partial eclipse happens. If it perfectly aligns, a total eclipse happens — but only for a few minutes, until the moon's orbit moves it past the sun. (Always use proper safety equipment to view a solar eclipse (opens in new tab).)
If you missed this penumbral eclipse, you can catch three more opportunities in 2020: June 5, July 5 and Nov. 30. The last 2020 eclipse will have the deepest darkening of the trio. All four lunar eclipses in 2020 are of the penumbral variety; the next total lunar eclipse isn't until May 26, 2021. Check out our lunar eclipse viewing guide (opens in new tab) to check if your location will experience the eclipse. If not, you can always catch the show online at Space.com.
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- How to Catch the Next Eclipse: A List of Solar and Lunar Eclipses in 2020 and Beyond
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As for last night's penumbral eclipse, I was happy to experience perfectly clear skies while watching it six hours past sunset, high in the sky, from Sweden at 60 N 15 E, and at 6 Centigrades below freezing.
Although I was trying my best to discern the darkening of the full Moon. I certainly would not have been able to distinguish this penumbral eclipse full Moon from any other full Moon without prior knowledge of this event. Even at that I cannot say with certainty that I noticed the difference, although I believe I did. This is my first attempt to observe a penumbral eclipse event, so I am not an experienced observer of such events, and in addition my vision is not as perfect as I would wish it would be.
Because of my interest in ancient reports of celestial events, my above question is very important to me. So please, if anyone has any insight whatsoever that may in any way serve as an answer to my above question, kindly share with me whatever you may have!